1. Field of the Invention
The present invention relates to a scroll compressor, and particularly, to an apparatus for preventing a vacuum state in a scroll compressor which can prevent the inside of a hermetic container from being vacuumized and facilitate an operation for preventing the vacuumization.
2. Description of the Background Art
In general, a compressor converts electric energy to kinetic energy and compresses a refrigerant gas by the kinetic energy. The compressor is a core factor which constitutes a refrigerating cycle system, and is classified into a variety of kinds such as a rotary compressor, a scroll compressor, a reciprocal compressor and the like. Such compressors are commonly used for a refrigerator, an air conditioner, a show case and the like.
FIG. 1 shows one example of the scroll compressor. As shown, the scroll compressor includes: a hermetic container 10; a main frame 20 and a sub frame 30 fixedly coupled to upper and lower portions of the hermetic container 10, respectively; a driving motor 40 positioned between the main frame 10 and the sub frame 20 and fixedly coupled to the inside of the hermetic container 10; a fixed scroll 50 fixedly coupled inside the hermetic container 10 at a certain interval between itself and the main frame 20; an orbiting scroll 60 placed between the fixed scroll 50 and the main frame 20 and orbiting in a state of being interlocked with the fixed scroll 50; a rotary shaft 70 transferring a driving force of the driving motor 40 to the orbiting scroll 60; an Oldham ring 80 inserted between the orbiting scroll 60 and the main frame 20, for preventing self-rotation of the orbiting scroll 60; and a high and low pressure separation plate 90 for separating an internal space of the hermetic container 10 into a high pressure space (H) and a low pressure space (L).
A suction pipe 1 for suction of a gas and a discharge pipe 2 for discharge of a gas are coupled to the hermetic container 10. The suction pipe 1 is placed at the low pressure space (L), and the discharge pipe 2 is placed at the high pressure space (H). The low pressure space (L) of the hermetic container 10 is a space where a gas is sucked, and the high pressure space (H) is a space where the compressed is discharged. Oil to be supplied to a sliding portion is filled in a lower portion of the hermetic container 10.
The fixed scroll 50 is provided with a body portion 51 having a predetermined shape; a wrap 52 formed at a lower portion of the body 51 as an involute shape; and a discharge hole 53 penetratingly formed at the center of the of the body 51.
The orbiting scroll 60 includes: a circular plate portion 61 having a predetermined area; a wrap 62 formed at an upper surface of the circular plate portion 61 as an involute shape; and a boss portion 63 formed at a lower surface of the circular plate 61.
The driving motor 40 comprises: a stator 42 fixedly coupled to an inner circumferential surface of the hermetic container 10; a winding coil 43 wound around the stator 42; and a rotor 44 rotatably inserted in the stator 42.
The rotary shaft 70 is provided with an eccentric portion 71. The rotary shaft 70 is pressingly inserted in the rotor 44 and is penetratingly inserted in the main frame 50, so that its eccentric portion 71 is inserted in the boss portion 63 of the orbiting scroll.
Undescribed reference mark 100 is a backflow preventing means for preventing backflow of a discharge gas.
The operation of the scroll compressor having such a structure will now be described.
First, the driving motor 40 is operated upon receiving power. When the rotary shaft 70 rotates upon receiving a rotary force of the driving motor 40, the orbiting scroll 60 coupled to the eccentric portion 71 of the rotary shaft orbits centering on the center of the rotary shaft 70. The orbiting scroll 60 does not rotate due to the Oldham ring 80 but orbits.
As the orbiting scroll 60 orbits, the wrap 62 of the orbiting scroll orbits in a state of being interlocked with the wrap 52 of the fixed scroll. Thus, a plurality of compression pockets (P) are formed by the wraps 62 and 52 of the orbiting scroll and the fixed scroll, and move to center portions of the fixed scroll 50 and the orbiting scroll 60, and the volumes of the compression pockets (P) are changed, thereby sucking and compressing a gas and discharging the compressed gas through the discharge hole 53 of the fixed scroll.
The compression pockets (P) are continuously formed as the orbiting scroll 60 orbits. When positioned at an edge of the fixed scroll 50, the compression pockets (P) are in a low pressure state, which is suction pressure, and when positioned at the center of the fixed scroll 50, the compression pockets (P) are in a high pressure state, which is discharge pressure. Also, when positioned between the edge and the center of the fixed scroll 50, they are in a middle pressure state.
High temperature high pressure gas discharged through the discharge hole 53 of the fixed scroll flows outside the hermetic container 10 through the high pressure space (H) of the hermetic container 10 and the discharge pipe 2.
The scroll compressor constitutes a refrigerating cycle system. In the refrigerating cycle system, the high temperature high pressure gas discharged from the scroll compressor by the operation of the scroll compressor passes through a condenser, a capillary tube and an evaporator. The gar having passed through the evaporator is introduced into the scroll compressor, and such circulation processes are repeated.
Meanwhile, if the operation of the scroll compressor is continued in a state that a gas is blocked and thus is not sucked into the hermetic container 10 of the scroll compressor through the suction pipe 1 because of problems occurring in the refrigerating cycle system or in a suction side of the scroll compressor, the low pressure space (L) of the hermetic container 10 is maintained in a vacuum state. If the low pressure space (L) of the hermetic container 10 is vacuumized, vacuum discharge is generated at a terminal portion placed at the low pressure space (L) side of the hermetic container 10 and connected to the driving motor 40, thereby causing the compressor to be damaged. Particularly, if the terminal and an insulation coating connected to the terminal become defective, the probabilities of vacuum discharge are raised.
Also, because the driving motor 40 is positioned in the low pressure space (L) of the hermetic container 10, if the low pressure space (L) of the hermetic container is maintained in the vacuum state, heat generated at the driving motor 40 is not effectively transmitted to the outside. For this reason, the driving motor 40 is over-heated, thereby causing the insulation film of a wire to be damaged.
Many researches are actively ongoing in order to solve such problems. As one of methods for solving the problems, a connecting passage allowing the high pressure space (H) and the low pressure space (L) of the hermetic container 10 to communicate with each other is provided, and a valve which reacts to a gas temperature of the high pressure space (H) of the hermetic container 10 is provided at the connecting passage side. When the high pressure space (H) of the hermetic container 10 is at a set temperature or higher, the valve reacts to the temperature and opens the connecting passage. In such a manner, the high pressure space (H) and the low pressure space (L) of the hermetic container 10 communicate with each other, thereby preventing vacuumization of the low pressure space (L) of the hermetic container 10.
However, such a method is disadvantageous in that if more than a certain pressure does not work on the connecting passage, operation of the valve is degraded or is not made at all.